Exercise treadmills are widely used in spas, exercise clubs and also in individual residences to enable users to walk, jog or run indoors. This is especially useful during inclement weather and also at night or at other times when exercisers do not desire to run outdoors. Most exercise treadmills include first and second roller assemblies that are transversely mounted at the ends of a frame. An endless belt is trained about the roller assemblies. The upper run of the belt is supported by an underlying deck positioned between the belt and the frame.
Efforts have been made to reduce the impact on the user's limbs and joints when jogging or running on a treadmill. One method of reducing the impact on an exerciser's body is disclosed by U.S. Pat. Nos. 4,974,831 and 4,984,810. In the treadmills disclosed by these patents, the rear end of the deck is pivotally mounted to the frame, with the forward end of the deck supported by a suspension system. In the '831 patent, the suspension system consists of a fairly complicated lever arm assembly and cooperating shock absorbers. Striding on a deck results in pivoting of the lever arms and extension of the shock absorbers, thereby to dampen the impact of the user's feet. A drawback of this shock absorption system is its complex nature, rendering it costly to manufacture.
In the '810 patent, the forward end of the treadmill deck was supported by a conventional compression spring and separate shock absorber. Placement of the spring and shock absorber at the very front of the deck imposes considerable bending stress on the deck.
Other conventional treadmills have utilized rubber blocks positioned between the deck and the underlying frame to absorb impact. One such conventional treadmill is disclosed in French Patent No. 2,616,132. A treadmill deck is mounted above the frame members on a plurality of flexible pads. Bushings are inserted into the top and bottom of each pad, and bolts depending downwardly from the deck and upwardly from frame are received within the corresponding bushings. The bolts serve to position the flexible pads between the deck and frame for shock absorption.
U.S. Pat. Nos. 5,336,144 and 5,454,772 disclose a deck supported above a frame by a plurality of cup-shaped elastomeric springs. The elastomeric springs reversibly deform during downward deflection of the deck toward the frame. The elastomeric springs have side walls of tapering thickness. As a result, the resistance to the downward travel of the deck provided by the elastomeric springs is proportional to the degree of deflection of the deck toward the frame. One drawback of this particular treadmill construction is that the elastomeric springs are fixed in place and individually define a rather small bearing area.